Experimental Cementation of Carbonate Sands: ABSTRACT

The processes of and diagenesis in carbonate rocks have been simulated in the laboratory by using CO2 charged water to leach a bed of carbonate sand. Precipitation of carbonate cement in a second sand body, above and below an artificial water table, was induced by CO2 evasion. Aragonite and high-Mg calcite (predominantly the latter) were leached from the source bed, and low-Mg calcite was precipitated as cement in the second sand unit. More cement was produced in the vadose zone than in the phreatic zone. The petrography of the cement is similar to that observed in cemented eolianites in Bermuda. Petrographic evidence suggests that cementation proceeds in 3 stages: (1) intragranular calcite cement forms drusy cavity fillings in the original voids of skeletal fragments; (2) rim cementation, consisting of fine-grained spar calcite; and (3) intergranular fine-grained calcite spar filling the original pore space in the skeletal sediment. Mass transfer calculations show that the laboratory cementation process is consistent with soil PCO2, rainfall, and cementation rates on Bermuda. End_of_Article - Last_Page 367------------